pumps and dumps are not made by miners, but by wallstreet creeps and devs, also ICO investors
I mined dbix, and i still have have the coins, not much, but when i see difficulty increasing at wrong percentage, i realise the devs either have no clues, or malice, so i went back to eth and stuff.
you had few times mining farms with 500GH/s - 1TH/s and they dumped the price not just once